Strlen introduction, and the difference between sizeof

Catalog

One ： Definition

Two ： give an example

3、 ... and : and sizeof Comparison

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One ： Definition

strlen function ： This function calculates the number of characters in the string starting from the first character , Until an empty character is encountered '\0' until , Then return the length of the calculated number of characters , Include '\0'.

Two ： give an example

int main()
{
	char s[]=("123456789 ");// Notice that I typed an extra space here , Indicates that spaces are also valid characters 
	int ch = strlen(s);
	cout << strlen(s) << endl;
	return 0;
}

  This means that strlen Is the number of valid characters of the string returned .

3、 ... and : and sizeof Comparison

int main()
{
	char s[]=("123456789 ");
	int ch = strlen(s);
	cout <<"strlen Length under :"<< strlen(s) << endl;
	cout << "sizeof Length under :"<<sizeof(s) << endl;
	return 0;
}

  Comparison results ：

sizeof The calculation will '\0' It's included , Is the string length +'\0'（+1）,strlen Just calculate the string length .